The present invention relates to solvent-free, two-component, polyurethane reactive compositions (2C-PUR) modified with special soft resins, for the production hydrophobic coatings that have good elongation, withstand cathodic protection and have long term temperature resistance.
To protect oil and gas pipelines, and also the ballast tanks of ships, from corrosion, coatings are required that are highly hydrophobic, are impact-resistant, have good elongation and withstand cathodic protection. Fusion bonded epoxide (FBE) systems, applied as a primer (optionally 2 coats) are known for coating pipelines. Here the powder is reacted on the hot pipe. The FBE coating is coated with polyethylene/polypropylene (PE/PP) by the sintering process, or a coating is built up with adhesive, PU foam and polyethylene. PUR systems applied as wet coatings both to the cold pipe or the field joints also known in the prior art. The pre-coated pipes are bent on site before incorporation into the pipeline network.
A disadvantage of the prior art is that the FBE coatings are brittle and do not have either stone impact resistance or elongation. The bending stresses arising when laying pipelines lead to the formation of cracks in the coating and thus the loss of corrosion protection. FBE systems can be applied for repairs on site or to coat field joints only at great cost (higher energy requirement) and with low productivity. EP-Wet systems cannot be used on site below 0xc2x0 C. The disadvantages of the pure some cases have lower tolerance of cathodic protection. The hydrophilic properties of the 2C-PUR systems require layer thicknesses of  greater than 1000 xcexcm for corrosion protection of pipes and ballast tanks.
An object of the present invention is to provide solvent-free, liquid primers for the corrosion protection of pipes, which
a) have a long term temperature resistance of up to 30xc2x0 C. and at the same time withstand cathodic protection,
b) have an elongation at break of at least  greater than 5% and are impact resistant,
c) provide long term protection even in thinner coats of 600-900 pm because they are more hydrophobic,
d) can be applied both on site and in a workshop, and cure at temperatures below 0xc2x0 C.,
e) can be used both for the pipe and for the field joints and
f) have a longer pot life (up to 15 minutes) and a longer surface-working time (up to 50 minutes).
These objects may be achieved with the polyurethane reactive compositions of the present invention as described hereinafter.
The present invention relates to a solvent-free, two-component polyurethane coating composition that is suitable for the production of coatings that have long term resistance to temperatures of to 30xc2x0 C., have good elongation and withstand cathodic protection, which contains
A) a solvent-free polymer mixture containing
I) 5 to 50 wt. % of a component free from OH groups and containing
a) 0 to 100 wt. % of a chlorinated paraffin or dibutoxybenzene,
b) 0 to 100 wt. % of a di-[phenoxy-alkyl]formal,
c) 0 to 100 wt. % of a polyacrylonitrile,
wherein the percentages of I-a), I-b) and I-c) add up to 100 wt. %, based on the weights of I-a) to I-c), and
II) 50 to 95 wt. % of a component having hydroxyl groups comprising
a) 40 to 100 wt. % of a component which contains hydroxy groups and ether groups, has a functionality of  greater than 3.5 and a number average molecular weight of 280 to 1000, and is different from b),
b) 0 to 60 wt. % of a hydroxy-functional polyether polyacrylate and
c) 0 to 60 wt. % of a hydroxy-functional compound other than a) and b),
wherein the wt. % of 11-a) to 11-c) add up to 100 wt. %, based on the weight of component 11) and
B) a polyisocyanate component comprising at least one organic polyisocyanate, wherein the NCO:OH equivalent ratio is 0.8:1 to 1.5:1.
In accordance with the present invention component 1) of solvent-free polymer mixture A) preferably contains
d) a mixture of a) and b) wherein the weight ratio of a):b) is 99:1 to 1:99,
e) a mixture of a) and c) wherein the weight ratio of a):c) is 99:1 to 1:99
or
f) a mixture of b) and c) wherein the weight ratio of b):c) is 99:1 to 1:99.
Suitable OH group-free components I-a) include chlorinated paraffins such as Hordaflex(copyright), Types LC and SP, (Hoechst), Cerechlor(copyright), Types 70/42 (ICI), Rishichlor(copyright) (Rishiroop), or polychlorodibutoxybenzene (Rishiroop).
Suitable components I-b) include di(phenoxy-ethyl)formal such as Desavin(copyright) (Bayer).
Suitable components I-c) include polyacrylonitriles having a average molecular weight of 600 to 3000.
Suitable components II-a), which contain hydroxyl groups, are polyether polyols, which can be obtained by known in known manner by the addition of cyclic ethers (such as ethylene oxide, propylene oxide, styrene oxide, butylene oxide or tetrahydrofuran) to starter molecules (such as polyvalent alcohols, aminoalcohols or amines free from ether groups, which have a number average molecular weight of 280 to 1000, preferably 350 to 700 and more preferably 400 to 500. The functionality of the starter molecules, with regard to the reaction with cyclic ethers, must be xe2x89xa73.5, preferably xe2x89xa74. Polyethers, which contain at least 50%, preferably at least 90%, based on the weight of the repeating units, of xe2x80x94CH(CH3)CH2O group, are especially preferred.
Polyvalent alcohols suitable for use as starter molecules include glycerine, trimethylolpropane, butanetriol-(1,2,4), hexanetriol-(1,2,6), bis(trimethylolpropane), pentaerythritol, mannitol or methylglycoside.
Suitable aminoalcohols include 2-aminoethanol, diethanolamine, 3-amino-1-propanol, 1-amino-2-propanol, diisopropanolamine, 2-amino-2-hydroxymethyl-1,3-propanediol and mixtures thereof.
Suitable polyvalent amines include aliphatic or cycloaliphatic amines, such as ethylene diamine, 1,2-diaminopropane, 1,3-diamino-propane, 1,4-diaminobutane, 1,3-diamino-2,2-dimethylpropane, 4,4-diaminodicyclohexyl-methane, isophorone diamine, hexamethylene diamine, and 1,12-dodecane diamine; aromatic amines such as the isomers of toluylene diamine; and mixtures thereof.
Polyhydroxy component II-b), which is optionally present in the binder mixture according to the invention, can be produced e.g. according to EP-A 825210 (U.S. Pat. No. 6,130,285, herein incorporated by reference).
Suitable alcohol components 11-c) have a (number average) molecular weight of 32 to 1000, preferably 32 to 350. Examples include methanol, ethanol, propanol, butanol, hexanol, 2-ethylhexanol, cyclohexanol, stearyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propanediol-1,2 and -1,3, dipropylene glycol, tripropylene glycol, butanediol-1,2, -1,3 -1,4 and -2,3, pentanediol-1,5,3-methylpentanediol-1,5, hexanediol-1,6,2-ethylhexanediol-1,3,2-methylpropenediol-1,3, 2,2-dimethylpropanediol-1,3,2-butyl-2-ethylpropanediol-1,3,2,2,4-trimethylpentanediol-1,3, octanediol-1,8, higher molecular weight xcex1-alkanediols containing 9 to 18 carbon atoms, cyclohexanedimethanol, cyclohexanediol, glycerine, trimethylolpropane, butanetriol-1,2,4, hexanetriol-1,2,6, bis(trimethylolpropane), pentaerythritol, mannitol and methylglycoside are preferred.
The hydroxy polyesters, hydroxy polyester amides, hydroxy polyethers having a functionality of  less than 3.5, polythioether polyols, hydroxy polycarbonates and hydroxy polyacetals having a number average molecular weight of up to 1,000, which are known from polyurethane chemistry, can optionally also be used as component II-c).
Known stabilizers from coatings technology, such as antioxidants and light stabilizers, can optionally be added to polymer mixture A) to further improve the light- and weather stability of the polyether polyacrylates. The binder mixtures according to the invention are preferably used without stabilizers.
Suitable antioxidants include stearically-hindered phenols such as 4-methyl-2,6-di-tert.-butylphenol (BHT) or other substituted phenols, thioethers (e.g. Irganox PS(copyright), Ciba Geigy) or phospites (e.g. Irgaphos(copyright), Ciba Geigy) available from Ciba Geigy under the product class name Irganox(copyright). Suitable light stabilizers include HALS (Hindered Amine Light Stabilizers) such as Tinuvin(copyright) 622 D or Tinuvin(copyright) 765 (Ciba Geigy); and substituted benzotriazoles, such as Tinuvin(copyright) 234, Tinuvin(copyright) 327 and Tinuvin(copyright) 571 (Ciba Geigy).
Polyhydroxy component 11 contains 40 to 100 wt. % of component II-a), 0 to 60 wt. % of component II-b) and 0 to 60 wt. % of component II-c). The sum of components II-a) to II-c), without taking account of any antioxidants or light stabilizers, is 100 wt. %.
Polyisocyanate component B) according to the invention is an organic polyisocyanate having an average NCO functionality of at least 2 and a molecular weight of at least 140. Suitable polyisocyanates include (i) unmodified organic polyisocyanates having with a molecular weight of 140 to 300, (ii) lacquer polyisocyanates having a number average molecular weight of 300 to 1,000, also (iii) urethane group-containing NCO pre polymers having a number average molecular weight of  greater than 1,000, and mixtures thereof.
Examples of polyisocyanates i) include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-d iisocyanatohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI), 1-isocyanato-1-methyl-4-(3)-isocyanatomethyl-cyclohexane, bis-(4-isocyanatocyclohexyl)methane, 1,10-diisocyanatodecane, 1,12-diisocyanatodecane, cyclohexane-1,3- and 1,4-diisocyanate, xylylene diisocyanate isomers, 2,4- and 2,6-diisocyanatotoluene or mixtures thereof preferably containing, based on the mixture, up to 35 wt. % 2,6-diisocyanatotoluene, 2,2xe2x80x2-, 2,4xe2x80x2-, 4,4xe2x80x2-diisocyanatodiphenylmethane or polyisocyanate mixtures of the diphenylmethane series and mixtures of the preceding isocyanates. The polyisocyanates of the diphenylmethane series, in particular as isomer mixtures, are preferred.
Suitable polyisocyanates ii) include the known solvent-free lacquer polyisocyanates. Within the context of the invention, the term xe2x80x9clacquer polyisocyanatesxe2x80x9d is understood to mean compounds or mixtures of compounds, which are obtained, by oligomerizing diisocyanates 1) in known manner.
Suitable oligomerization reactions include allophanatization, biuretization, carbodiimidization, cyclization, dimerization, urea formation, trimerization and/or urethanization. xe2x80x9cOligomerizationxe2x80x9d often refers to several of the stated reactions taking place concurrently or consecutively. xe2x80x9cLacquer polyisocyanatesxe2x80x9d are preferably polyisocyanates containing uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione groups.
The production of lacquer polyisocyanates is known and disclosed, for example, in DE-A 1 595 273, DE-A 3 700 209, DE-A 3 900 053, EP-A-0 330 966, EPAO 259 233, EP-A-0 377 177, EP-A-0 496 208, EP-A-0 524 501 and U.S. Pat. No. 4,385,171.
The urethane group-containing lacquer polyisocyanates ii) can be obtained by the reaction of low molecular weight polyhydroxyl compounds with excess quantities of the preceding di- or polyisocyanates by using a large excess of the di- and polyisocyanates and subsequently removing the excess polyisocyanate, e.g. by thin layer distillation. The prepolymers are preferably produced at 40 to 140xc2x0 C., optionally using suitable catalysts.
Suitable polyhydroxyl compounds for preparing the prepolymers are those having a molecular weight of 62 to 299, such as ethylene glycol, propylene glycol-1,3, butanediol-1,4, hexanediol-1,6, neopentylglycol, 2-ethylhexanediol-1,3, glycerine, trimethylolpropane, pentaerythritol, low-molecular weight esters of these polyols with dicarboxylic acids (such as those disclosed hereinafter), low molecular weight ethoxylation or alkoxylation products of these polyols and mixtures thereof.
Polyisocyanates iii) are the known prepolymers having isocyanate groups and prepared by reacting diisocyanates i) and/or lacquer polyisocyanates ii) with organic polyhydroxyl compounds having a number average molecular weight greater than or equal to 300. These polyhydroxyl compounds are known and preferably have a number average molecular weight of 300 to 20,000, more preferably 1,000 to 8,000.
Suitable high molecular weight polyhydroxyl compounds for the production of the prepolymers include polyester polyols prepared from the low molecular weight alcohols previously described and polybasic carboxylic acids such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, the anhydrides of these acids and any mixtures thereof. Polylactones having hydroxyl groups, in particular polycaprolactones, are also suitable for the production of the prepolymers.
Polyether polyols, such as those obtained in the known manner by the alkoxylation of suitable starter molecules, are also suitable for the production of the NCO prepolymers. Suitable starter molecules are the low molecular weight polyols previously described, water, organic polyamines with at least two Nxe2x80x94H bonds and mixtures there. Alkylene oxides suitable for the alkoxylation reaction are preferably ethylene oxide and/or propylene oxide, which can be used in any order or in admixture in the alkoxylation reaction.
Polytetramethylene glycol polyethers, such as those obtained in known manner by cationic polymerization of tetrahydrofuran, are also suitable for the production of the prepolymers.
Polycarbonates having hydroxyl groups, such as those prepared, for example, by the reaction of low molecular diols with phosgene or diaryl carbonates such as diphenylcarbonate, are also suitable for the production of the prepolymers.
Polythioetherpolyols, such as those obtained, for example, by the polycondensation of the thiodiglycol with itself, or with diols and/or polyols, are also suitable for the production of prepolymers having NCO groups.
Polyacetals, such as polycondensation products of formaldehyde and diols or polyols that can be obtained using acid catalysts (e.g., phosphoric acid or p-toluenesulfonic acid), are also suitable for the production of prepolymers having NCO groups.
Mixtures of the preceding polyhydroxyl compounds can also be used to produce the prepolymers.
To produce the coating compositions according to the invention, components A) and B) are mixed with each other in amounts sufficient to provide an NCO:OH equivalent ratio of 0.8:1 to 1.5:1, preferably 0.9:1 to 1.3:1.
Known additives from coatings technology may optionally be added. Examples include levelling agents, viscosity-controlling additives, pigments, fillers, matting agents, UV stabilizers, antioxidants and catalysts for the crosslinking reaction. These compounds are normally added to and mixed with component A) before components A) and B) are mixed together.
The solvent-free, long term temperature resistant, two-component polyurethane coatings according to the invention can be used to protect any metal substrate, even under cathodic protection conditions at long term temperature loads of up to 30xc2x0 C. The metallic substrates are preferably sheet pilings, locks, ships, pipes and other metal objects in the marine, offshore and onshore industries.
The invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.